FullSimplify[2 c Conjugate[c]]
2 c Conjugate[c]
This seems strange to me. For some reason, a third entry in the Times precludes the simplification with Abs. Is this just a shortcoming of the way FullSimplify is implemented, or is there some good reason for this?
It's quite annoying when I have a complicated expression and some terms are real and positive definite, but this is not immediately obvious, because FullSimplify is failing to combine variables with their complex conjugates.